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The effect of histone deacetylase inhibitors on SRC and BCL2L1 gene expression and a potential role for phosphatases in their transcriptional repression2013 August 1900 (has links)
Histone Deacetylase Inhibitors (HDACi) are a new class of chemotherapeutics which have shown promise in pre-clinical and clinical settings. HDACi have been shown to act by re-programming gene expression, with the transcription of some genes such as p21WAF1 being activated, while others like SRC and BCL2L1 are repressed. The mechanism behind HDACi gene expression changes remains unknown; although it has been shown to involve a direct interaction with gene promoters.
Using a quantitative qRT-PCR approach, the effect of various HDACi on the transcription of p21WAF1, SRC and BCL2L1 was examined. TSA and apicidin led to an up regulation of p21WAF1 mRNA levels while c-Src and Bcl-xL mRNA levels were downregulated. Short c-Src mRNA transcripts were unaffected following TSA and apicidin treatments, despite the full length transcripts being repressed. Repression of full length c-Src and Bcl-xL mRNA transcripts was not seen following treatment with MS-275 and MGCD0103, although p21WAF1 mRNA expression was induced. ChIP experiments revealed that following HDACi treatment, histone acetylation levels and RNA Polymerase II occupancy increased in the promoter regions of both the SRC and BCL2L1 genes. RNA Polymerase II occupancy lasted less than 15 minutes in the 3’ regions of the gene following treatment with apicidin and TSA, but was more long-term following MS-275 and MGCD0103 treatment. The protein phosphatase inhibitor Calyculin A completely blocked HDACi mediated repression of c-Src and Bcl-xL mRNA, suggesting a role for protein phosphatases in the mechanism behind HDACi.
It is therefore hypothesized that HDACi work through at least two different mechanisms. Whether or not an HDACi leads to gene repression depends on its ability to disrupt an HDAC/protein phosphatase complex and not on their HDAC specificities. The disruption of the complex leads to the release of an active protein phosphatase. The released phosphatase can then presumably act on various factors changing a gene from an active to paused state, possibly through promoter proximal pausing. HDACi unable to disrupt this complex are unable to induce gene repression. Collectively, these studies highlight not only the complexity of HDACi mediated effects within the cell, but also present a new explanation behind HDACi mediated gene repression.
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The Design and Synthesis of Novel Barbiturates of Pharmaceutical InterestNeumann, Donna 21 May 2004 (has links)
Barbituric acids have been historically classified as compounds that act on the central nervous system, and as such provide therapeutic uses as anxiolytics, sedatives, hypnotics, and anticonvulsants. Recent investigations of barbituric acid derivatives have provided scientists with information that barbituric acids may have applications in antibacterial, anti-chlamydial, anti-viral, as well as anti-cancer treatments. Additionally, recent literature accounts have indicated that barbituric acid derivatives may also act as immune modulators. The recent explorations of barbiturates and their potential anti-cancer and immune modulating properties are the subject of this work. Novel synthetic approaches to the development of new barbituric acid derivatives were explored thoroughly, and the mechanisms of these novel syntheses were detailed by experiment and spectroscopic characterizations. In many cases the reaction procedures were designed for large scale, efficient syntheses, that are directly applicable to pharmaceutical production of these potentially valuable therapeutic compounds. Several new products unique to barbituric acid reactions were characterized spectroscopically. Barbituric acid derivatives were the subject of biological evaluation, and the results are reported in this work. Overall, unique synthetic approaches to the production of novel barbituric acid derivatives were accomplished to create several new classes of barbiturates with potential applications in cancer treatment.
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Transcriptional regulation of the SRC12 and SRC1A promoters in human cancer cell linesDehm, Scott Michael 25 August 2003
The human SRC gene encodes pp60c-Src (or c-Src), a 60 kDa, non-receptor tyrosine kinase frequently activated in colon and other tumors. Many studies have demonstrated c-Src activation can be accounted for by overexpression of c-Src protein, and that this overexpression is important for the fully transformed phenotype of cancer cells. The general goal of this thesis, therefore, was to determine the mechanism of this overexpression in human cancer cells. Examination of c-Src expression and activity in human colon cancer cell lines showed that c-Src activation was due to transcriptional activation of the SRC gene. SRC transcription is directed by the ubiquitous, Sp1 regulated SRC1A promoter, and the HNF-1alpha regulated, tissue restricted SRC1alpha promoter. To study the mechanism of SRC transcriptional activation in human cancer cell lines, a dual SRC promoter reporter construct was generated with both these promoters in their natural, physiologically linked context. Very low activity of the SRC1alpha promoter, relative to SRC1A, was consistently observed from this construct, leading to the conclusion that an enhancer element elevates SRC1alpha promoter activity. Interestingly, the HNF binding site in the SRC1alpha promoter enhanced SRC1A promoter activity in the dual promoter construct, but only in a colon cancer cell line with activated SRC. These results therefore suggest SRC transcriptional activation results from enhancer action and/or SRC promoter cross-talk in subsets of human cancer cells. <p> This study has also determined that histone deacetylase inhibitors (HDIs), compounds with documented anti-neoplastic properties, repress transcription from both SRC promoters in various cancer cell lines. To identify the mechanism of this repression, various deletion and mutant SRC promoter constructs were assayed, but HDI response elements were not identified. However, it was discovered that both promoters shared a common requirement for functional TAF1/TAF(II)250, a component of the general transcription factor TFIID. Compromised TAF1 function impaired SRC transcription, but also blocked SRC repression by HDIs. Experiments with SRC:WAF1 promoter chimeras showed the SRC promoters' TAF1 requirement could be conferred on the heterologous, TAF1-independent promoter for the WAF1 gene, which encodes the cell cycle inhibitor p21. These chimeras were also repressed by HDIs, despite WAF1 normally being strongly induced by these agents. These results therefore provide a potential functional link between promoter architecture, TAF1 dependence, and HDI mediated transcriptional repression.
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Transcriptional regulation of the SRC12 and SRC1A promoters in human cancer cell linesDehm, Scott Michael 25 August 2003 (has links)
The human SRC gene encodes pp60c-Src (or c-Src), a 60 kDa, non-receptor tyrosine kinase frequently activated in colon and other tumors. Many studies have demonstrated c-Src activation can be accounted for by overexpression of c-Src protein, and that this overexpression is important for the fully transformed phenotype of cancer cells. The general goal of this thesis, therefore, was to determine the mechanism of this overexpression in human cancer cells. Examination of c-Src expression and activity in human colon cancer cell lines showed that c-Src activation was due to transcriptional activation of the SRC gene. SRC transcription is directed by the ubiquitous, Sp1 regulated SRC1A promoter, and the HNF-1alpha regulated, tissue restricted SRC1alpha promoter. To study the mechanism of SRC transcriptional activation in human cancer cell lines, a dual SRC promoter reporter construct was generated with both these promoters in their natural, physiologically linked context. Very low activity of the SRC1alpha promoter, relative to SRC1A, was consistently observed from this construct, leading to the conclusion that an enhancer element elevates SRC1alpha promoter activity. Interestingly, the HNF binding site in the SRC1alpha promoter enhanced SRC1A promoter activity in the dual promoter construct, but only in a colon cancer cell line with activated SRC. These results therefore suggest SRC transcriptional activation results from enhancer action and/or SRC promoter cross-talk in subsets of human cancer cells. <p> This study has also determined that histone deacetylase inhibitors (HDIs), compounds with documented anti-neoplastic properties, repress transcription from both SRC promoters in various cancer cell lines. To identify the mechanism of this repression, various deletion and mutant SRC promoter constructs were assayed, but HDI response elements were not identified. However, it was discovered that both promoters shared a common requirement for functional TAF1/TAF(II)250, a component of the general transcription factor TFIID. Compromised TAF1 function impaired SRC transcription, but also blocked SRC repression by HDIs. Experiments with SRC:WAF1 promoter chimeras showed the SRC promoters' TAF1 requirement could be conferred on the heterologous, TAF1-independent promoter for the WAF1 gene, which encodes the cell cycle inhibitor p21. These chimeras were also repressed by HDIs, despite WAF1 normally being strongly induced by these agents. These results therefore provide a potential functional link between promoter architecture, TAF1 dependence, and HDI mediated transcriptional repression.
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Therapeutic potential of demethylation agents and histone deaceytlase inhibitors in NK-cell lymphoma and leukemiaKam, Kevin., 甘季燐. January 2007 (has links)
published_or_final_version / Medical Sciences / Master / Master of Medical Sciences
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Activation of lytic cycle of Epstein-barr virus of histone deacetylaseinhibitorsHui, Kwai-fung., 許貴鋒. January 2008 (has links)
published_or_final_version / Paediatrics and Adolescent Medicine / Master / Master of Philosophy
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Effects of Histone Deacetylase Inhibitors on the Maintenance of Midbrain Neurons and GliaForgione, Nicole Louise 21 August 2012 (has links)
Perturbations of the complex intrinsic and extrinsic factors that contribute to cellular differentiation can have many consequences ranging from dedifferentiation to cell death. The overall objective of my research is to investigate the factors that contribute to the maintenance of mature midbrain neurons and glia. In order to address this objective, I first carried out a detailed immunocytochemical analysis to demonstrate that histone deacetylase inhibitor (HDACI) treatment of differentiated midbrain neurons in culture results in an overall destabilization of neuronal phenotype, which leads to caspase-independent cell death. GFAP positive astrocytes are refractory to the effects of HDACI treatment, suggesting that inhibition of HDACs has differential effects on neurons and glia. HDACI treatment alone was not sufficient to induce neuronal dedifferentiation as evidenced by RT-PCR analysis of stem/progenitor markers, and recovery experiments. Finally, I demonstrate that cortical neurons do not undergo cell death in response to HDACI treatment, suggesting that there may be microenvironmental factors that promote the susceptibility of midbrain neurons to the neurotoxic effects of HDACI. In the second part of this thesis I determined the molecular mechanism that was at least partly responsible for the effects of HDACI treatment on midbrain neurons. Gene expression profiling of HDACI treated midbrain cultures revealed a strong down-regulation of immune related factors. This observation is supported by the loss of microglia in HDACI treated midbrain cultures. I also provide evidence that Toll-like receptor (TLR) signaling, likely through the activation of Interleukin-6 (IL-6) expression, mediates HDAC-dependent neuronal survival. These data provide new evidence that the neuroimmune system is an extrinsic regulator for the homeostasis and survival of neurons.
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A novel mechanism of chemoprevention by sulforaphane : inhibition of histone deacetylaseMyzak, Melinda C. 29 April 2005 (has links)
Targeting the epigenome, including the use of histone deacetylase (HDAC)
inhibitors, is a novel strategy for cancer chemoprevention. Sulforaphane
(SFN), a compound found at high levels in broccoli and broccoli sprouts, is a
potent inducer of Phase 2 detoxification enzymes and inhibits tumorigenesis
in animal models. SFN also has a marked effect on cell cycle checkpoint
controls and cell survival/apoptosis in various cancer cells, through
mechanisms that are poorly understood. Based on the structure of known
histone deacetylase inhibitors, it was hypothesized that SFN may possess
HDAC inhibitory properties. Initial studies confirmed that, indeed, at
physiologically-relevant concentrations, SFN inhibited HDAC activity in
human colorectal cancer cells, with a concomitant increase in acetylated
histones H3 and H4, induction of p21 expression, and increased acetylated
histone H4 associated with the P21 promoter. A metabolite of SFN, SFN-Cysteine,
was found to be the active HDAC inhibitor. Furthermore, in BPH-1,
LnCaP, and PC-3 human prostate epithelial cells, SFN inhibited HDAC
activity and increased acetylation of histones. SFN also induced p21
expression, with an increase in acetylated histone H4 associated with the P21
promoter in BPH-1 cells. The downstream effects of HDAC inhibition by SFN
included induction of pro-apoptotic proteins and repression of anti-apoptotic
proteins, and an increase in multi-caspase activity. Dietary SFN suppressed
the growth of human prostate cancer PC-3 xenografts and inhibited HDAC
activity in the xenografts, peripheral blood mononuclear cells (PBMC), and
prostates. In time-course studies, a single oral dose of SFN induced histone
acetylation at 6 and 24 h in mouse colonic mucosa, and long-term dietary
SFN treatment increased histone acetylation in the ileum, colon, PBMC, and
prostates. Moreover, dietary SFN suppressed intestinal tumorigenesis
significantly in Apc[superscrip min] mice, with an increase in acetylated histones detected
in the normal-looking ileum and polyps and polyps from the colon. Overall,
the data presented in this thesis support a novel mechanism for
chemoprevention by SFN in vivo, through inhibition of histone deacetylase.
The findings also imply that SFN will offer significant protection against at
least two of the major cancer killers in the US, namely colon and prostate
cancer. / Graduation date: 2005
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Determining the Activity of Three HDAC Variants in the Presence of Compounds Containing 1,2,3-and 1,2,4-Triazoles as Zinc Binding GroupsGlazener, Rachel Louise 01 August 2010 (has links)
Histone Deacetylase (HDAC) plays a vital role in cellular processes, for example gene expression, cell growth, and apoptosis. Finding drug candidates to inhibit the over activity of HDACs in cancer is a growing area of interest. Inhibitors, thus far, have three important motifs to be studied: the zinc binding group, a hydrophobic linker, and a cap group. By altering these groups on the inhibitor, not only can activity be increased but also selectivity within the classes of HDACs. We present the design of two novel sets of molecules that contain either a 1,2,3-triazole or 1,2,4-triazole. The 1,2,3-triazoles were synthesized using “click chemistry” with a novel pyridyl triazine catalyst. The 1,2,4-triazoles were synthesized utilizing substitution chemistry. This set of molecules was designed after suberoylanilide hydroxamic acid (SAHA) but replaced the hydroxamate with the triazole as the zinc binding group. The activity of these inhibitors against HDAC 1, HDAC 6, and SIRT 1 were tested using the Biomol Fluor de Lys in vitro kits. Though none of the synthesized compounds were strong activators or inhibitors of any of the classes of HDACs, trends were observed that could lead to the design of more potent inhibitors.
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Determining the Activity of Three HDAC Variants in the Presence of Compounds Containing 1,2,3-and 1,2,4-Triazoles as Zinc Binding GroupsGlazener, Rachel Louise 01 August 2010 (has links)
Histone Deacetylase (HDAC) plays a vital role in cellular processes, for example gene expression, cell growth, and apoptosis. Finding drug candidates to inhibit the over activity of HDACs in cancer is a growing area of interest. Inhibitors, thus far, have three important motifs to be studied: the zinc binding group, a hydrophobic linker, and a cap group. By altering these groups on the inhibitor, not only can activity be increased but also selectivity within the classes of HDACs. We present the design of two novel sets of molecules that contain either a 1,2,3-triazole or 1,2,4-triazole. The 1,2,3-triazoles were synthesized using “click chemistry” with a novel pyridyl triazine catalyst. The 1,2,4-triazoles were synthesized utilizing substitution chemistry. This set of molecules was designed after suberoylanilide hydroxamic acid (SAHA) but replaced the hydroxamate with the triazole as the zinc binding group. The activity of these inhibitors against HDAC 1, HDAC 6, and SIRT 1 were tested using the Biomol Fluor de Lys in vitro kits. Though none of the synthesized compounds were strong activators or inhibitors of any of the classes of HDACs, trends were observed that could lead to the design of more potent inhibitors.
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